trace tcp_output.c:1550
  commands
    collect $reg
  end
disable
trace /home/teawater/big/kernel/tb/18/linux-2.6.18.i686/net/ipv4/tcp_output.c:1529
  commands
    collect ((struct tcp_sock *)sk)->rx_opt.rcv_wscale
    collect ((struct tcp_sock *)sk)->rcv_ssthresh
    collect ((struct tcp_sock *)sk)->window_clamp
    collect sk->sk_rcvbuf
    collect sk->sk_rmem_alloc
  end
